With $4 gas, what do you get for mileage??????

1997 Ram club cab, sb 2wd. 318 headers, new cat, magnaflow exhaust, e fan, tonneau cover
Best is 17 city 20 MPG highway, even with the OD, the thing needs another gear, anything over 65 and it is turning more RPM then it wants to

Dart Lite.... Not sure yet....hopefully well into 20's